High flow sensors generally use a bypass flow channel in combination with a main flow channel. A laminar flow element (LFE) may be incorporated in the main flow channel. A typical LFE may include multiple parallel flow channels with relatively small cross-sectional area to laminarize the main flow and create a pressure restriction. The bypass flow channel is fluidly communicated to the main flow channel via taps that are disposed perpendicular to the main flow channel. The taps may include a first tap and a second tap, with the first tap disposed upstream of the LFE and the second tap disposed downstream of the LFE.
The perpendicular orientation of the taps presents static pressure at the taps. The difference in the static pressure between the first and second taps drives flow through the bypass flow channel. The flowrate through the bypass flow channel may be controlled by features of the bypass, such as length and diameter, or an orifice or tube shaped feature may be used to limit bypass flow rate.
Disposing the taps upstream and downstream of the LFE places the taps where a large flow volume is available for redirection into the bypass flow channel. However, this arrangement can exhibit certain drawbacks. First, with this arrangement the taps are placed in a more turbulent, large diameter flow zone, and flow agitation from turbulence increases signal noise. Second, the flow passing through the geometry changes at the inlet and outlet of the LFE can create unstable flow and pressure changes at the taps, which can adversely affect sensor signal. Third, non-linear orifice effects that are inherent in restricting flow through the bypass can create non-linear output and a reduction in signal in lower flow ranges.
Hence, there is a need for a flow sensor that addresses the above-noted drawbacks, and/or creates a bypass flow rate with minimal components and size, and/or implements a relatively long bypass flow channel to reduce orifice effects caused by differences in relationship of cross-sectional area of the bypass channel to the partitions in the LFE. The present invention addresses at least these needs.